Hi Rob and Phil,
The recording was made in a rural setting, but there was significant
breeze in the tree canopy, so that will clearly have some effect. But
that does not explain what sounds like a LF plusing in the recording.
I made a short recording last night in almost dead clam conditions
hand holding the rig, and there are massive levels of LF energy present.
I want to investigate what is going on a bit more fully but it does
sound to me like some kind of LF oscillation similar to what Phil has
found. I'll hook up the mic and recorder to a 'scope at some stage
today and see if I can pinpoint what is happening.
I'm using HD280's for field monitoring, and I've been checking
recordings with them at home as it's the only way I can get an idea
of what is happening in the bottom end. They are quite nice phones ;)
cheers
Paul
On 03/03/2008, at 3:52 AM, Rob Danielson wrote:
> Hi Phil-
> Sorry. I think I may have confused your application with the 3032's
> and the Mix Pre and Paul's.
>
> Phantom powering could be a factor, but Paul seems to be connecting
> his mics directly to the HDP2. If so, we're getting down to unusual
> suspects. It seems unlikely that both 3032's would arrive at his
> doorstep with _matching_ poor frequency response. That leaves cables,
> recorder/recorder settings and the mic rig as suspects. The high
> frequencies could be attenuated by essentially "blanketing" the mics
> with excessive wind protection, but this would be inconsistent with
> the lack of mic self-noise (hiss) in Paul's sample. I assume Paul's
> HDP2 was at or near full mic preamp gain in that location.
>
> Thanks for the nod about preserving low Hz content. In the sample we
> are studying, the sonogram from Rich's "quiet" rural setting, shows
> how much of the sound energy resides below 125Hz:
> https://pantherfile.uwm.edu/type/public/media/
> RichAT3202_PaulAT3202.jpg
>
> I suspect some recordists use the low cut filter to make it easier to
> hear the high frequency content/calls in the field, but its possible
> to bring home a fuller spectrum and still experience good monitoring
> by using fully-enclosed headphones. Sennheiser HD280 phones, for
> example, cost $90USD and provide about 30dB attenuation. Of course,
> the low frequencies can always be shaped in post. Rob D.
>
> = = = =
>
> At 9:49 AM +0000 3/2/08, Phil Tyler wrote:
>> Hi Paul
>>
>> Just a thought I have a pair of AT3032's which I use with a Sound
>> Devices MixPre.
>>
>> I found that the MixPre became unstable when using AT3032's due to
>> the way in which
>> they work with phantom power. Most phantom power mic's vary the
>> voltage they draw
>> depending on the signal. AT3032's vary the current and this is what
>> causes the Sound
>> Devices MixPre the problem, due to the way it is itself powered.
>> This low frequency
>> instability was reduced using the LF cut on the MixPre.
>> But I found another, much better, way around the problem, as the
>> AT3032's are current
>> and not voltage dependent they have quite a wide voltage range they
>> can run on. So
>> switching my MixPre to 15 volt phantom, rather than the normal 48
>> volt and my problem
>> goes away. As the MixPre's power supply can cope using the lower
>> phantom voltage, and I
>> can record without any LF cut, as Rob tells me I should :-))
>>
>> It may be your system is exhibiting a similar problem but not
>> actually becoming fully
>> unstable?
>>
>> Hope you find a solution soon.
>>
>> Phil
>>
>> --- In
>> <naturerecordists%
>> 40yahoogroups.com>
>> Paul Jacobson <> wrote:
>>>
>>> Ok I guess I should post an illustration of what I'm getting.
>>>
>>> The whroo frogs recording which I posted to the list, and to which
>>> John referred to, was made with LF cut on the HDP2 switched on. I
>>> initially started recording with LF Cut off and had the recorder
>>> running when I flipped the switch. There isn't much happening in
>>> the
>>> recording apart from a bit of rustling, but it clearly illustrates
>>> the kind of LF energy or "growl" that I'm trying eliminate.
>>>
>>>
>>> <http://www.urbanbirder.com.au/audio/play/13>http://
>>> www.urbanbirder.com.au/audio/play/13
>>>
>>> I'm trying to identify what is contributing to that LF energy. My
>>> suspicion is that resonances from the tripod are being transmitted
>>> into the rig, but looking at sonograms of Walt's comparative
>>> recordings seemed to suggest that the might mic be a contributing
>>> factor as well, but that could very well be a misinterpretation of
>>> the recordings. I certainly wasn't condemning the AT3032's to the
>>> junk heap - in fact I'm about to order another to use in a Telinga
>>> Universal rig.
>>>
>>> I'm sure it's been stated many times, that these rigs are
>>> experimental
>>>
>>> The main reason I am looking at this is that I want to tweak/
>>> rebuild
>>> the rig before I head up to the Alice Springs area in May for a
>>> couple of weeks. The top priority is incorporating a shock
>>> mounting,
>>> which I hope will eliminated much of the LF rumble/growl.
>>>
>>> cheers
>>> Paul
>>>
>>>
>>> On 02/03/2008, at 4:38 PM, Rob Danielson wrote:
>>>
>>>> Paul,
>>>> Sorry to hear your AT3032's are not performing up to your
>>>> expectations. I second John's suggestion. If you are certain the
>>>> abnormal response or artifact lies in the lower registers, it would
>>>> help to select a sound from (or record a test in) a quiet location
>>>> away from low frequency sound sources. It common for locations to
>>>> have lots of energy in this part of the spectrum. A wooden barrier
>>>> can lift the upper mid-range and brighten-up the sound a bit,
>>>> but it
>>>> typically does not emphasize the lows. Of course, if you have other
>>>> mics you can make recordings with in the same location/conditions,
>>>> they'll will provide additional reference. Rob D.
>>>
>>
>>
>
>
> --
>
>
>
>
>
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> sound is worth a thousand pictures." R. Murray Schafer via Bernie
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